1. Field of the Invention
This invention relates to a novel polymeric peroxy ester, which is useful as a free radical-generating agent to be used for vinyl monomer, and a method for producing a polymer having a high molecular weight and further having a high mechanical strength by the use of the polymeric peroxy ester.
2. Related Art Statement
There has been known a diacyl type polymeric peroxide obtained by the polycondensation reaction of dibasic acid chloride with sodium peroxide. That is, Ber., Vol. 27, page 1,510 (1984) discloses that the reaction of a phthalic acid chloride with sodium peroxide results in a corresponding diacyl type polymeric peroxide, and Chem. Abst. Vol. 60, 5,293d (1964) and Vol. 60, 10,892e (1964) disclose that the reaction of an aliphatic dibasic-acid chloride with sodium peroxide results in a diacyl type polymeric peroxide represented by the following general formula: ##STR4## wherein n represents a positive integer of 2-10 and x represents a positive integer of 16-35. Japanese Patent Laid-open Specification N o. 53,149,918 discloses a diacyl type polymeric peroxide having ester linkages, which has been obtained by the reaction of a dibasic-acid chloride having ester linkages in its molecule with sodium peroxide. Japanese Patent Laid-open Specification Nos. 59-38,233, 59-93,725, 59-176,320 and 59-227,904 disclose diacyl type polymeric peroxides obtained by the reaction of a dibasic acid having branched or unsaturated hydrocarbon groups in its molecule with sodium peroxide.
Zh. Org. Khim., Vol. 13, No. 9, page 1,842 (1977) discloses that an aliphatic or aromatic dibasic acid chloride with 2,5-dimethylhexane-2,5-dihydroperoxide results in a corresponding polymeric peroxy ester. U.S. Pat. No. 3,117,166 specification discloses that the reaction of phthalic acid- or fumaric acid-chloride with 2,5-dimethylhexane-2,5-dihydroperoxide results in a corresponding polymeric peroxy ester.
It is commonly known that these diacyl type polymeric peroxides or polymeric peroxy esters are effective as a polymerization initiator for vinyl monomer. For example, it is reported in Chem. Abst., Vol. 67, 54,445a (1967) that, when the above described polymeric peroxide is used as a polymerization initiator, a polymer having a molecular weight as high as two times that of a polymer obtained by the use of benzoyl peroxide can be obtained. Further, it is reported in Chem. Abst., Vol. 84, 136,120f (1976) that, when the above described polymeric peroxide is used as a polymerization initiator for vinyl acetate, a polymer, which is larger in the molecular weight and is less in the amount of branches than a polymer obtained by the use of benzoyl peroxide, can be obtained.
Further, it is known that, in the production of vinyl polymer, when a polymer having a high average molecular weight is produced, the object of obtaining a polymer having a high mechanical strength can be attained. In general, a polymer having a high average molecular weight can be obtained by decreasing the use amount of polymerization initiator or lowering the polymerization temperature, but such procedure lowers noticeably the polymerization rate, that is, productivity, and hence such procedure is not a commercially available method.
In order to obviate these drawbacks, Japanese Patent Laid-open Specification Nos. 53-28,685 and 54-107,994, Japanese Patent Application Publication No. 58-56,561, Japanese Patent laid-open Specification Nos. 60-206,809, 60-206,810 and 60-185,512 and recent Japanese Patent Laid-open Specification No. 62-54,704 disclose embodiments, wherein a polymer having a high molecular weight or having a high mechanical strength is produced by the use of a specifically limited bifunctional peroxide or trifunctional peroxide having 2 or 3 peroxy bonds respectively in one molecule. Further, Japanese Patent Laid-open Specification Nos. 60-8,304, 60- 13,805 and 60-152,517 disclose the production of a polymer having a high mechanical strength by the use of a specifically limited diacyl type polymeric peroxide, which has a structural unit represented by the following formula ##STR5## and has 3 or more of peroxy bonds in one molecule.
Further, there is known a method, wherein a combination of at least 2 kinds of polymerization initiators is used, as one of the methods for obtaining a polymer having a high molecular weight without decreasing the polymerization rate. For example, Japanese Patent Application Publication No. 49-20,944 discloses a method, wherein a combination of 3 kinds of initiators is used and further the polymerization temperature is raised corresponding to the proceeding of polymerization. Japanese Patent Laid-open Specification No. 54-107,994 discloses the use of a specifically limited bifunctional peroxide as a polymerization initiator.
As described above, although both the conventional diacyl type polymeric peroxide and polymeric peroxy ester are useful polymerization initiators in the production of a polymer having a high molecular weight from a vinyl monomer, such as styrene, acrylonitrile or the like, or a mixture thereof, or in the production of block copolymers, such as styrenemethyl methacrylate block copolymer, styrene-vinyl acetate block copolymer and the like. However, the conventional diacyl type polymeric peroxide or polymeric peroxy ester has the following drawbacks. (1) The former diacyl type polymeric peroxide is generally very poor in the solubility in various organic solvents (refer to Chem. Abst., Vol. 59, 7,651 (1963)), or is a sensitive compound, which is sensitive to impact and friction (refer to Chem. Abst., Vol. 64, 15,989g (1968) and Koka-shi, Vol. 69, page 718 (1966)), and it is difficult to use the diacyl type polymeric peroxide for commercial purpose. Further, diacyl type polymeric peroxides free from the above described drawbacks are disclosed in Japanese Patent Laid-open Specification Nos. 59-38,233, 59-93,725, 59-176,320 and 59-227,904. These diacyl type polymeric peroxides have a 10-hour half-life period temperature within the range of 60-70.degree. C. When a vinyl monomer or a mixture thereof is polymerized by the use of the diacyl type polymeric peroxide, a vinyl polymer having a high molecular weight can be obtained, or when 2 kinds of vinyl monomers are block-polymerized by the use of the diacyl type polymeric peroxide, a so-called block copolymer can be obtained. However, in order to increase the polymerization rate and to improve the productivity of the polymers, a high polymerization temperature is necessary. For this purpose, it is necessary to use a diacyl type polymeric peroxide having a 10-hour half-life period temperature of 70-85.degree. C., preferably 75-85.degree. C., which is a little higher than the above described 10-hour half-life period temperature of 60-70.degree. C., and the development of such diacyl type polymeric peroxide has been desired.
(2) Although the latter polymeric peroxy ester has an activity at high temperature, substantially all of the polymeric peroxy esters have a high melting point, are solid (refer to U.S. Pat. No. 3,117,166), are sensitive to impact and friction, and are very poor in the solubility in various organic solvents. Therefore, it is very difficult to use the polymeric peroxy ester as a polymerization initiator in commercial scale.
In the method for producing a polymer by the use of the conventional bifunctional peroxide or trifunctional peroxide, a polymer having a satisfactorily high molecular weight or a polymer having a satisfactorily high mechanical strength has not yet been obtained. In the method for producing a polymer by the use of the above described specifically limited diacyl type polymeric peroxide, a polymer having a somewhat high molecular weight can be obtained, but the polymerization rate is low. Further, even when the polymerization temperature is raised in the use of the diacyl type polymeric peroxide, the increase of the polymerization rate is small, and the molecular weight of the resulting polymer is reversely low. For example, although the use of the bifunctional peroxide or diacyl type polymeric peroxide in the production of a polymer containing o-methylstyrene unit is known, the resulting polymer has not yet a satisfactorily high mechanical strength. Therefore, the development of an improved polymerization initiator capable of increasing the productivity of a polymer and capable of producing a resin having a more improved performance has been demanded.